1. Field of the Invention
The present invention relates to a light emitting device, and more particularly, to a light emitting device for use in a backlight module of a liquid crystal display (LCD).
2. Descriptions of the Related Art
A liquid crystal display utilizes a liquid crystal panel to display. Since liquid crystal panels do not emit light by itself, it is necessary to equip them with light sources having enough brightness and uniform light. Through guiding the emitted light efficiently and adequately, liquid crystal panels can display images with high qualities. Providing quality light is through a backlight module.
In view of the positions of light sources relative to display panels, backlight modules are usually categorized into edge-type lighting modules and bottom-type lighting modules. There are many types of light sources as well, including Light Emitting Diode (LED). By adopting various light sources and providing them at different positions of the light guiding plate, people can create many different light emitting devices.
FIG. 1A and FIG. 1B illustrate a light emitting device of a blacklight module of the prior art. The light emitting device comprises a light guiding plate 12 and a set of light sources 13 (i.e. a plurality of LEDs). The light guiding plate 12 comprises a light incident surface 121 and a light outgoing surface 122, which is adjacent to and is approximately perpendicular to the light incident surface 121. The light outgoing surface 122 comprises an active display area. The set of light sources 13 faces the light incident surface 121, whose emitted light enters into the light guiding plate 12 through the light incident surface 121 and exits though the light outgoing surface 122 after certain reflections and refractions. However, light emitting angles of the set of light sources 13 (especially point light sources like LEDs) are usually between 90 to 110 degrees and makes regions of the active display area, where the light incident surface 121 is adjacent, form dark areas due to less incident light. The situation usually occurs at the regions of the corners of the panel and areas between point light sources. It degrades the degree of the uniformity of the light guiding plate 12.
A technique illustrated in FIG. 1C tries to reduce the aforementioned dark area by introducing a curved concaved area 123 to increase the scattering angle of the emitted light of the set of light sources 13. However, the improvement is still limited.